1. Field of the Invention
This invention relates generally to oil lubricating systems for aircraft engines, and pertains more particularly to a system for achieving a rapid warm-up of the oil in just a short interval after a cold engine has been started.
2. Description of the Prior Art
In oil lubricating systems for piston-type aircraft engines, it is customary to have a main oil tank installed from which the oil is gravitationally delivered to the engine, the oil then being returned from the engine to the tank for reuse. Thus, the oil continually circulates through the tank. After a period of time, the oil becomes warm and it is also conventional to make use of an oil cooler or radiator so that some or all of the oil can be passed through the cooler in order to prevent the oil temperature from becoming too hot.
However, especially in northern climates, small propeller-operated aircraft experience extremely low temperatures with the consequence that the internal combustion engine, and also the oil within the lubricating system, becomes quite cold and viscous. To reduce the degree of viscosity, it has been quite common to introduce into the oil a suitable diluent, such as alcohol, so that the combined liquid can flow more readily. As the lubricant containing the diluent becomes heated, then the diluent, especially if it is an alcohol and therefore volatile, vaporizes, thereby ultimately leaving the oil in virtually the same condition as it was originally. While procedures such as this have produced generally acceptable results, it is a nuisance for the pilot to be concerned with the adding of a diluent and, quite obviously, he must not introduce too much. Also, care must be exercised not to introduce too much at a given time, it being necessary to control the rate of adding the diluent. Also, the adding of diluent must be discontinued at the appropriate time, and sometimes this delays takeoff, and if provision is made for discontinuing the adding of a diluent after takeoff, the system becomes rather complex and quite costly.